1. Technical Field
The present invention relates to an oscillator, an electronic apparatus, and a moving object.
2. Related Art
A crystal oscillator, which is used for a reference frequency signal source for communication equipment, a measurement instrument, or the like, is required to have the output frequency stable with high accuracy with respect to a temperature variation. In general, there is known an oven controlled crystal oscillator (OCXO) as a crystal oscillator capable of providing an extremely high frequency stability among crystal oscillators (JP-A-2014-197751 (Document 1)). The OCXO has a quartz resonator housed in an oven controlled in a constant temperature, and in order to realize the extremely high frequency stability, it is important to decrease the temperature control deviation of the oven with respect to the variation in the ambient temperature as much as possible.
FIG. 16(A) described in Document 1 is a diagram showing an example of a frequency-temperature characteristic in the case in which the temperature control of the oven is not performed in the OCXO using an SC-cut crystal resonator, and FIG. 16(B) and FIG. 16(C) are diagrams showing a part surrounded by a dotted line in FIG. 16 (A) in an enlarged manner. In the case in which, for example, the operating temperature range of the OCXO is −40° C. through +85° C., it is possible to output a stable frequency small in deviation even with a variation in the ambient temperature by keeping the temperature of the oven in the vicinity of 90° C. Although the accuracy of the oven varies between the products, in the case in which, for example, the temperature of the oven changes as much as ±2° C. around a peak of 90° C. when the ambient temperature varies up to a range of −40° C. through 85° C., the frequency deviation is about 20 ppb. In contrast, in the case in which the temperature of the oven, which is set to 90° C., actually becomes 92° C. shifted as much as 2° C., if the temperature of the oven changes as much as ±2° C. around the peak of 92° C., the frequency of the OCXO has a second-order temperature characteristic, and the frequency deviation becomes 40 ppb.
Further, an oscillation circuit and a frequency adjustment circuit also has a temperature characteristic, and the temperature characteristic has a variety of properties such as a contribution to linear reduction in frequency of the OCXO with respect to rise in temperature. Therefore, since the temperature characteristic of an electronic component of the oscillation circuit or the like is superimposed on the second-order frequency-temperature characteristic, in the OCXO of the related art, there is a problem that it is difficult to satisfy the requirement of the extremely high frequency stability.